Effect of mechanical drying air conditions on quality of turmeric powder.

Mother and finger rhizomes 'PCT-8' ('Suvarna') variety of turmeric (Curcuma longa L) were boiled separately in open pan for 45 min at 100°C. The rhizomes were then dried using tray drier at air temperatures of 45, 50, 55, 60 and 65°C and drying air velocities of 1, 2 and 3 m/sec. The rhizomes were dried to ∼10 % (wb) moisture content. The dried rhizomes were polished manually and powdered. The volume of fresh and dried turmeric was determined and shrinkage ratio calculated. The colour of fresh and dried turmeric was determined. Change in colour (ΔE) with drying time was found to be 2.3 and 2.7 for fingers and mothers respectively at 60°C and 2 m/sec air velocity. The oleoresin content was 13.0 and 12.0% for fingers and mothers, respectively. The drying of turmeric took place in the falling rate period and was governed by moisture diffusion. The best quality turmeric was obtained by drying at 60°C air temperature and 2 m/sec air velocity.